This invention relates generally to load responsive system controls, which permit variation in the level of control differential between pump discharge pressure and the load pressure signal, while this control differential is automatically maintained constant at each controlled level.
In more particular aspects this invention relates to load responsive system controls, which permit variation in the controlled pressure differential between pump discharge pressure and the load pressure, in response to an external control signal.
In still more particular aspects this invention relates to signal modifying controls of a load responsive system, which supply control signals to output flow control of a pump, to adjust and regulate the pressure differential across an orifice positioned between the system pump and a fluid motor operating a load.
Load responsive systems, in which pump output flow controls respond to load pressure signal to maintain a constant pressure differential between pump discharge pressure and load pressure, are well known in the art. In such a control system flow through an orifice, positioned between system pump and fluid motor operating a load, is proportional to the area of the orifice and independent of system load. Such load responsive systems are very desirable for a number of reasons. Not only do they provide exceptional control of a load, but they permit operation of the load at very high system efficiency. Such load responsive fluid control systems are shown in U.S. Pat. No. 2,892,312 issued to Allen et al and my U.S. Pat. No. 3,444,689 dated May 20, 1969. One disadvantage of such systems is the fact that, once the control pressure differential is selected and incorporated into system design, it will remain constant under all operating conditions of the system. Adjustment of the controlled level of the system differential, in respect to system flow, pressure, or specific conditions relating to control of a load, would not only improve the control characteristics of the system, improve the system efficiency, but would also make possible independent adjustments in the system performance, while the system load is controlled by a load responsive direction control valve.